Transformers

Which of the following acts as a protection against high voltage surges due to lightning and switching ?

A. Horn gaps
B. Thermal overload relays
C. Breather
D. Conservator

A good voltage regulation of a transformer means________________?

A good voltage regulation of a transformer means
A. output voltage fluctuation from no load to full load is least
B. output voltage fluctuation with power factor is least
C. difference between primary and secondary voltage is least
D. difference between primary and secondary voltage is maximum

Which of the following protection is normally not provided on small distribution transformers ?

A. Overfluxing protection
B. Buchholz relay
C. Overcurrent protection
D. All of the above

For a transformer, operating at constant load current, maximum efficiency will occur at______________?

A. 0.8 leading power factor
B. 0.8 lagging power factor
C. zero power factor
D. unity power factor

A Transformer transforms____________?

A. voltage
B. current
C. current and voltage
D. power

A transformer can have regulation closer to zero___________?

A. on full-load
B. on overload
C. on leading power factor
D. on zero power factor

In a transformer the resistance between its primary and secondary should be_____________?

A. zero
B. 10 Q
C. 1000 Q
D. infinity

The secondary of a current transformer is always short-circuited under operating conditions because it____________________?

A. avoids core saturation and high voltage induction
B. is safe to human beings
C. protects the primary circuit
D. none of the above

A shell-type transformer has_________?

A. high eddy current losses
B. reduced magnetic leakage
C. negligibly hysteresis losses
D. none of the above

N atural air coo ling is generally restricted for transformers up to__________?

A. 1.5 MVA
B. 5 MVA
C. 15 MVA
D. 50 MVA